Area active backlight with steerable light source

ABSTRACT

A liquid crystal display includes a backlight. The backlight includes a plurality of waveguides to selectively direct light. A set of selection elements in combination with the backlight selectively direct light to the front of the display.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/322,115, filed Jan. 28, 2009.

BACKGROUND OF THE INVENTION

The present invention relates to a liquid crystal panel, and inparticular to a liquid crystal panel with a steerable light source.

The local transmittance of a liquid crystal display (LCD) panel or aliquid crystal on silicon (LCOS) display can be varied to modulate theintensity of light passing from a backlit source through an area of thepanel to produce a pixel that can be displayed at a variable intensity.Whether light from the source passes through the panel to an observer oris blocked is determined by the orientations of molecules of liquidcrystals in a light valve.

Since liquid crystals do not emit light, a visible display requires anexternal light source. Small and inexpensive LCD panels often rely onlight that is reflected back toward the viewer after passing through thepanel. Since the panel is not completely transparent, a substantial partof the light is absorbed while it transits the panel and imagesdisplayed on this type of panel may be difficult to see except under thebest lighting conditions. On the other hand, LCD panels used forcomputer displays and video screens are typically backlit withfluorescent tubes or arrays of light-emitting diodes (LEDs) that arebuilt into the sides or back of the panel. To provide a display with amore uniform light level, light from these point or line sources istypically dispersed in a diffuser panel before impinging on the lightvalve that controls transmission to a viewer.

The transmittance of the light valve is controlled by a layer of liquidcrystals interposed between a pair of polarizers. Light from the sourceimpinging on the first polarizer comprises electromagnetic wavesvibrating in a plurality of planes. Only that portion of the lightvibrating in the plane of the optical axis of a polarizer can passthrough the polarizer. In an LCD the optical axes of the first andsecond polarizers are arranged at an angle so that light passing throughthe first polarizer would normally be blocked from passing through thesecond polarizer in the series. However, a layer of translucent liquidcrystals occupies a cell gap separating the two polarizers. The physicalorientation of the molecules of liquid crystal can be controlled and theplane of vibration of light transiting the columns of molecules spanningthe layer can be rotated to either align or not align with the opticalaxes of the polarizers.

The surfaces of the first and second polarizers forming the walls of thecell gap are grooved so that the molecules of liquid crystal immediatelyadjacent to the cell gap walls will align with the grooves and, thereby,be aligned with the optical axis of the respective polarizer. Molecularforces cause adjacent liquid crystal molecules to attempt to align withtheir neighbors with the result that the orientation of the molecules inthe column spanning the cell gap twist over the length of the column.Likewise, the plane of vibration of light transiting the column ofmolecules will be “twisted” from the optical axis of the first polarizerto that of the second polarizer. With the liquid crystals in thisorientation, light from the source can pass through the seriespolarizers of the translucent panel assembly to produce a lighted areaof the display surface when viewed from the front of the panel.

To darken a pixel and create an image, a voltage, typically controlledby a thin film transistor, is applied to an electrode in an array ofelectrodes deposited on one wall of the cell gap. The liquid crystalmolecules adjacent to the electrode are attracted by the field createdby the voltage and rotate to align with the field. As the molecules ofliquid crystal are rotated by the electric field, the column of crystalsis “untwisted,” and the optical axes of the crystals adjacent the cellwall are rotated out of alignment with the optical axis of thecorresponding polarizer progressively reducing the local transmittanceof the light valve and the intensity of the corresponding display pixel.Color LCD displays are created by varying the intensity of transmittedlight for each of a plurality of primary color elements (typically, red,green, and blue) that make up a display pixel.

Referring to FIG. 1, a liquid crystal display (LCD) 50 (indicated by abracket) comprises, a backlight 52 and a light valve 54 (indicated by abracket). Since liquid crystals do not emit light, most LCD panels arebacklit with fluorescent tubes or arrays of light-emitting diodes (LEDs)that are built into the sides or back of the panel. To disperse thelight and obtain a more uniform intensity over the surface of thedisplay, light from the backlight 52 typically passes through a diffuser56 before impinging on the light valve 54.

The transmittance of light from the backlight 52 to the eye of a viewer58, observing an image displayed on the front of the panel, iscontrolled by the light valve 54. The light valve 54 comprises a pair ofpolarizers 60 and 62 separated by a layer of liquid crystals 64contained in a cell gap between the polarizers. Light from the backlight52 impinging on the first polarizer 62 comprises electromagnetic wavesvibrating in a plurality of planes. Only that portion of the lightvibrating in the plane of the optical axis of a polarizer can passthrough the polarizer. In an LCD light valve, the optical axes of thefirst 62 and second 60 polarizers are typically arranged at an angle sothat light passing through the first polarizer would normally be blockedfrom passing through the second polarizer in the series. However, theorientation of the translucent crystals in the layer of liquid crystals64 can be locally controlled to either “twist” the vibratory plane ofthe light into alignment with the optical axes of the polarizers,permitting light to pass through the light valve creating a brightpicture element or pixel, or out of alignment with the optical axis ofone of the polarizers, attenuating the light and creating a darker areaof the screen or pixel.

The surfaces of a first glass plate 63 and a second glass plate 61 formthe walls of the cell gap and are buffed to produce microscopic groovesto physically align the molecules of liquid crystal 64 immediatelyadjacent to the walls. Molecular forces cause adjacent liquid crystalmolecules to attempt to align with their neighbors with the result thatthe orientation of the molecules in the column of molecules spanning thecell gap twist over the length of the column. Likewise, the plane ofvibration of light transiting the column of molecules will be “twisted”from the optical axis of the first polarizer 62 to a plane determined bythe orientation of the liquid crystals at the opposite wall of the cellgap. If the wall of the cell gap is buffed to align adjacent crystalswith the optical axis of the second polarizer, light from the backlight52 can pass through the series of polarizers 60 and 62 to produce alighted area of the display when viewed from the front of the panel (a“normally white” LCD).

To darken a pixel and create an image, a voltage, typically controlledby a thin film transistor, is applied to an electrode in an array oftransparent electrodes deposited on the walls of the cell gap. Theliquid crystal molecules adjacent to the electrode are attracted by thefield produced by the voltage and rotate to align with the field. As themolecules of liquid crystal are rotated by the electric field, thecolumn of crystals is “untwisted,” and the optical axes of the crystalsadjacent to the cell wall are rotated progressively out of alignmentwith the optical axis of the corresponding polarizer progressivelyreducing the local transmittance of the light valve 54 and attenuatingthe luminance of the corresponding pixel. Conversely, the polarizers andbuffing of the light valve can be arranged to produce a “normally black”LCD having pixels that are dark (light is blocked) when the electrodesare not energized and light when the electrodes are energized. Color LCDdisplays are created by varying the intensity of transmitted light foreach of a plurality of primary color (typically, red, green, and blue)sub-pixels that make up a displayed pixel. A set of color filters 84, apolarizer 82 arranged in front of the touch screen can significantlyreduce the reflection of ambient light, also a cover plate 86 may beplaced over the polarizer 82.

The aforementioned example was described with respect to a twistednematic device. However, this description is only an example and otherdevices may likewise be used, including, but not limited to,multi-domain vertical alignment (MVA), patterned vertical alignment(PVA), in-plane switching (IPS), and super-twisted nematic (STN) typeLCDs.

FIG. 2 illustrates a typical liquid crystal display 100 (i.e., LCD) witha side-lit cold cathode florescent light (i.e., CCFL) backlight lamp110. The light from the CCFL lamp 110 may be coupled into an opticalwaveguide 120. The emitted light is primarily confined in the opticalwaveguide 120 via total internal reflection (TIR) and scattering fromthe bottom surface 130 of the optical waveguide 120 causes the lightthat has a scattered angle less than the critical angle to pass throughthe front of the optical waveguide 120 and distribute generallyuniformly across the display. Unfortunately, the light provided by thebacklight 110 can not be selectively controlled to different regions ofthe display.

The foregoing and other objectives, features, and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention, taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates a liquid crystal display.

FIG. 2 illustrates a liquid crystal display with a side lit backlight.

FIG. 3 illustrates a liquid crystal display with an optical waveguide.

FIG. 4 illustrates a light extractor for a light emitting diodebacklight.

FIG. 5 illustrates TIR in a waveguide.

FIG. 6 illustrates FTIR in a waveguide.

FIG. 7 illustrates FTIR display.

FIG. 8 illustrates LCD backlight from 1D linear optical waveguide.

FIG. 9 illustrates a LCD backlight consisting of 1D backlight elements.

FIG. 10 illustrates a PSF.

FIG. 11 illustrates light steering using electrostatic FTIR.

FIG. 12 illustrates a flow chart for deriving LED and LCD driving valuesfor input to a display.

FIG. 13 illustrates tone mapping.

FIG. 14 illustrates a LCD backlight consisting of 1D backlight elementsand a transparent material based steering mechanism.

FIG. 15 illustrates the transparent material of FIG. 14 in an off state.

FIG. 16 illustrates the transparent material of FIG. 14 in an on state.

FIG. 17 illustrates the layers of the transparent material of FIG. 14.

FIG. 18 illustrates a polymer matrix with liquid crystals therein of thetransparent material of FIG. 14.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

It is desirable to include an active backlight which selectivelyprovides light to different regions of the display to improve the imagequality. Such regions of the display may be as small as a pixel, orsub-pixel, or a fraction of a sub-pixel, but in general aresignificantly larger than a pixel and are preferably patterned so thatit produces uniform light output for uniform input. In addition, beingable to selectively reduce the backlight in different regions of thedisplay also decreases the overall power consumption of the display.However, two dimensional backlights traditionally require a separatedriver for each active unit, which is relatively expensive for a largedisplay area.

A display may include a series (or plurality) of single light emittingdiodes arranged in a parallel fashion along the edge of the display, orother light sources, each of which provides illumination to aone-dimensional striped region across the display. The light sources maylikewise be arranged to illuminate regions of the display in any othermanner. Collectively, the one-dimensional illuminated regions illuminatethe entire display. In relation to a two-dimensional array of lightemitting diodes, the one-dimensional array of light emitting diodesresult in a lower cost for the display, but fail to include theillumination selectivity capable with the two-dimensional array.

After considering both the desirability of a two-dimensional array oflight sources together with low cost benefits of a one-dimensional arrayof light sources, it was determined that such two dimensional arraycapabilities with a one dimensional array are achievable by using anoptical waveguide together with a temporal based illumination techniquefor different regions of the display. This combination achieves both thebenefits of the selectivity of the two-dimensional array together withthe low cost and power reduction benefits of a one-dimensional array.Moreover, a spatially temporal illumination of pixels may also be usedto improve image quality, namely, a reduction in image blur when displaymoving objects, as well as increased contrast ratio from dark black. Thelight waveguide may be any type of structure that directs or otherwisesupports the passage of light from one location to another.

FIG. 3 illustrates a backlight that includes a LED light source. Lightfrom the LED is coupled into the waveguide and a light extractor isemployed to distribute light uniformly across the screen.

FIG. 4 illustrates the light extractor of FIG. 3. The circles in thefigures indicate the areas that no longer satisfy the TIR condition andaccordingly distribute the light into the LCD across the display. Thearea and distribution of these extractors are arranged to achieve agenerally uniform backlight.

In the backlight configurations illustrated in FIGS. 2, 3, and 4, thetotal internal reflection is used to guide the light from a light sourcesuch as CCFL, LED, or laser to the front of the display. Referring toFIG. 5, a TIR waveguide is illustrated. The TIR light guide may be madefrom a transparent polymer with a refractive index of 1.50 giving acritical angle of 41.8°. The light generated from LEDs enters the lightguide; the angular distribution of rays is bound within ±θ_(c).According to Snell's Law, all rays strike the interior wall at anglesgreater than θ_(c) will be totally internally reflected and will travelalong the light guide. This means that all beams incident on the inputface of the guide are guided.

There are many ways to extract the light from the waveguide. One way toextract light is to using scattering to change the direction of thelight ray such that the incident angle is less than the critical angleθ_(c). Another way to extract light is the have another material of ahigher, lower, or the same refractive index at a very close proximity(such as within a few wavelengths) of the waveguide so that theevanescent wave from the TIR couples to the new material (evanescentwave coupling). The evanescent wave coupling causes a frustrated totalinternal reflection (FTIR) which results in the extraction of light fromthe waveguide. FIG. 6 illustrates frustrated total internal reflectionin an optical waveguide. The light can thus be selectively extractedfrom an optical waveguide at desirable locations.

One technique for constructing a display that incorporates FTIR is touse one or more light guides at angles that maximize (or otherwise havesignificant TIR) the total internal reflection to reduce light fromescaping the backlight. Referring to FIG. 7, a thin film layer may beused to form a lens/shutter by sandwiching micro optic structures 200between two transparent conductors 210 and 220. The refractive indicesat the boundaries of the layers and surrounding the TFT structure on thelight guide approximate those of air to preserve total internalreflection. Bonding the layer to the slightly elevated TFT structurecreates a small air gap between the light guide and the film, thus thelayer tends to literally ride on the TFT elements of the display.

When oppositely charged at any given pixel, the two conductive layers210, 220 attract each other (as shown in FIG. 7). This pulls the microoptic structures down through the air gap until they contact the lightguide. Once a portion of the layer touches the light guide beneath, thetotal internal reflection becomes frustrated, thus permitting light toescape through the associated pixel at that location. The duration ofthe charge controls the opening and closing of the “shutter.” At anygiven pixel, this duration determines the relative intensity of theassociated pixel, sub-pixel, and/or color.

The use of a two dimensional area active backlight enables one or moreof the following advantages:

-   -   1. Increase in the contrast with reduced black level;    -   2. Reduced power consumption;    -   3. Motion blur reduction with backlight flashing; and    -   4. Wide color gamut with the use RGB backlight, and maintaining        the size of the color gamut with reduced brightness.

Unfortunately, two dimensional area active backlights require a largenumber of driving circuits. For an example, a backlight with 48×24×3backlight elements requires 3456 drivers, which can be prohibitivelyexpensive. Even more important is that the more back light elements, themore non-uniformity that may result together with the expensive of thephoto sensor circuits to compensate for the non-uniformity. Thus, it isadvantageous to reduce the number of back light elements.

One technique to reduce the number of back light elements (“BLEs”) is touse a one-dimensional linear backlight where each back light elementconsists of one or more LEDs and an optical waveguide that extendsacross a part of or the whole display. FIG. 8 illustrates a backlightwith ten one dimensional BLEs, each covering one vertical strip from topto bottom of the display. The use of a plurality of one dimensional BLEsreduces the number of drivers thus saving expense. Also, a plurality ofone-dimensional BLEs makes it easier to monitor and compensate fornon-uniform light output of the BLEs to achieve spatial uniformity andcolor consistency. While the use of a series of back light elementstogether with a light guide is an improvement, the advantages consistentwith two-dimensional backlights is not fully achieved, including, a highcontrast ratio, reduced power consumption, a wide color gamut at lowlight levels, and/or reduced motion blur from backlight flashing.

To achieve two-dimensional functionality with a set of one-dimensionallight sources, a light steering technique may be used to activelyextract light to enable a two-dimensional area active backlight fromone-dimensional linear or point light sources. The light from the LED orother light source is coupled into the optical waveguide, but the lightoutput from selected regions, such as that of one or more sets ofpixels, is scanned from top to bottom (or any other suitable addressingmechanism). For an example, a steering mechanism may steer the lightoutput from the top to the bottom as shown in FIG. 9. When one of thesteering devices is activated, the associated horizontal row in theoptical waveguide is open for light extraction; light is extracted fromthat row only and the other areas remains black. The activated lightsteering device may be de-activated and another light steering device isactivated. The associated horizontal row of the new activated lightsteering device results in the optical waveguide being open for lightextraction for that row while the other areas remains black. Thisprocess may be repeated for each light steering mechanism, preferably ina sequential manner. More than one light steering mechanism may besimultaneously selected, if desired. One or more of the light steeringmechanisms may be selected multiple times while presenting an image, ifdesired. The display may have light guides that extend over only a partof the width of the display, thus requiring multiple light guides tocover the width of the display, if desired. This light steering with thetemporal multiplexed driving results in a two dimensional area activebacklight using a one-dimensional waveguide. The point spread function(PSF) is horizontally defined by the one dimensional waveguide lightoutput profile, and vertically by the light output profile of thesteering. FIG. 10 illustrates an example PSF using a steerableone-dimensional backlight.

The steering mechanism may be achieved mechanically with a controllableshutter that is similar to the window shutter. Each of the lightsteering units is consisted of a motorized shutter. When a row isselected for light output, the motor opens the shutter to allow lightoutput for that horizontal row, then closes, and the next row shutteropens and so on. Although mechanical shutter may be used, it may pose anoise or life time issues.

A steering mechanism based on the evanescent wave coupling as shown inFIG. 6 is preferred. There are many ways to achieve evanescent wavecoupling. In most cases, a change in the refractive index near thewaveguide causes frustrated total internal reflection. Some techniquesto create FTIR include:

-   -   1. Electrostatic techniques where the TFT controls the electrode        so that the two layers with opposite charge attract each other.        The electrostatic force caused the two films to touch. Once the        two film touches, the light is coupled out as shown in FIG. 7.        In some cases, only a few light switches may be necessary to        achieve a desirable viewing experience.    -   2. Piezoelectric techniques where a voltage causes the coupling        film to touch the optical waveguide.    -   3. Electro-optical techniques where a voltage causes the        refractive index of the coupling film to increase thus reducing        the critical angle for TIR. In this case, there is no movement        of the coupling film, only a change in the refractive index.    -   4. Mechanical motor that rotates around that causes the coupling        film to touch the optical waveguide once per revolution.

As shown in FIG. 9, the optical waveguide may be arranged verticallyacross the display. The coupling light output from the waveguide may besynchronized with LCD driving, which is normally done from top tobottom, one line at a time. The light is steered out at the top, thennext row, until it reaches the bottom, and then repeats the process.FIG. 11 illustrates the light steering sequence for a backlight with 5steerable segments. At frame start, the first (top in the figure) row isselected for light output. The LED output intensity, or the pulse widthmodulation (PWM) width, or both the intensity and the PWM width aremodulated based on the desired backlight for that position. All theother areas are black. At ⅕^(th) the frame period (3.3 ms), the firstrow is de-selected which causes the coupling film to move away from thewaveguide, and the 2^(nd) row is selected which causes the coupling filmto move close to the waveguide so that FTIR occurs for the second row.The LED driving values that corresponds to the second row is loaded intothe LED drivers and all the LED light illuminates the area correspondingthe 2^(nd) row. The process is repeated for the 3^(rd), 4^(th) and5^(th) rows to complete one LCD frame. Alternatively, it is possiblethat the functions of the LEDs and the light steering may be reversed,if desired.

One advantage of this temporal multiplexed driving is the reducedtemporal aperture which reduces the motion blur. Each steerable row is“on” for only a fraction of the temporal period makes it an impulsivedisplay that can achieve blur reduced rendering of a motion sequence.

The above light steering can be applied for a point light source such asa laser with two dimensional steering. The light is first coupled to atwo dimensional waveguide with M (horizontal)×N (vertical) steerablebacklight elements. The light output is scanned from top to bottom andleft to right as it is done in a CRT display.

The steerable backlight is equivalent to an area active backlight with M(number of column drivers)×N (number of steerable units)×C (number ofcolor channels) backlight elements. FIG. 12 shows the flowchart of atechnique to convert an input image into a low resolution twodimensional backlight (steerable one dimensional backlight) and a highresolution LCD image. The LCD resolution is m×n pixels with its rangefrom 0 to 1, with 0 to be black and 1 to be the maximum transmittance.The backlight resolution is M×N with M<m and N<n. One may assume thatthe input image has the same resolution as LCD. If input image is ofdifferent resolution, a scaling or cropping step may be used to convertthe input image to LCD image resolution. The first step is to derive thedesired backlight from the input image.

The input image is low pass and sub-sampled (down sample) to anintermediate resolution of (M1×N1), one example is 8 times the BLEresolution (8M×8N). Extra resolution is useful to detect motion and topreserve the specular highlight. The maximum of the 8×8 sub-sampledimage forms the LEDmax Image (M×N). The block mean image is then tonemapped via an 1D LUT as shown in FIG. 13. The curve contains a darkoffset and expansion nonlinearity to make the backlight at dark regionslightly higher. This will reduced the visibility of dark noise andcompression artifacts. The maximum of the two is used as the targetbacklight value.

The target backlight has the same size as the number of active backlightelements (M×N). Flickering (i.e. intensity fluctuation) can be observedwhen an object moves across BLE boundaries. This boundary objectmovement causes an abrupt change in BLE driving value. Theoretically,the change in backlight can be compensated by the LCD. But due to timingdifference between the LED and LCD, and mismatch in the PSF used in thecalculation of the compensation and the actual PSF of that BLE, there issome small intensity variation. This intensity variation might not benoticeable when the eye is not tracking the object motion. But when eyeis tracking the object motion; this small backlight change becomesperiodic fluctuation. The frequency of the fluctuation is the product ofvideo frame rate and object motion speed in terms of BLE blocks perframe. If an object moves across a BLE block in 8 video frames and thevideo frame rate is 60 Hz, the flickering frequency is 60 hz*0.125=7.5Hz. This is about at the peak of human visual sensitivity to flickeringand it makes a very annoying artifact. To reduce this motion flickering,a motion adaptive algorithm may be used to reduce the sudden BLE outputchange when an object moves across the BLE grids. Motion detection isused to divide video image into two classes: motion region and stillregion. In the motion region, the backlight contrast is reduced so thatthere is no sudden change in BLE driving value. In the still region, thebacklight contrast is preserved to improve the contrast ratio and reducepower consumption.

Motion detection may be done at the subsampled image at M1×N1resolution. The value at current frame was compared to the correspondingblock in the previous frame. If the difference is greater than athreshold, then the backlight block that contains this block isclassified as motion block. In the preferred embodiment, each backlightblock contains 8×8 sub-blocks. The process of motion detection may be asfollows:

For each frame;

-   -   1. Calculate the average of each sub-block in the input image        for the current frame;    -   2. If the difference between the average in this frame and the        sub-block average of the previous frame is greater than a        threshold (for an example, 5% of total range), then backlight        block that contains the sub-block is a motion block. Thus a        first motion map is formed;    -   3. Perform a morphological dilation operation on the motion map        (change the still blocks neighboring to a motion block) to form        an enlarged motion map.    -   4. For each backlight block, the motion status map is updated        based on the motion detection results:        -   if it is motion block,            -   mMap(i,j)=min(4, mMap(i,j)+1);        -   else (still block)            -   mMap(i,j)=max(0, mMap(i,j)−1).

The LED driving value is given by

${L\; E\; {D_{2}\left( {i,j} \right)}} = {{\left( {1 - \frac{mMap}{4}} \right)L\; E\; {D_{1}\left( {i,j} \right)}} + {\frac{mMap}{4}L\; E\; {D_{\max}\left( {i,j} \right)}}}$

LED_(max) is the local max of LEDs in a window that centers on thecurrent LED. One example is a 3×3 window. Another example is a 5×5window.

Thus, it may be observed that in those regions that include non-motionthe energy is spit over two (or more) frames which reduces flickeringbut increases blur. However, without any significant motion there shouldbe no significant blur. Accordingly, it may be observed that in thoseregions that include motion the energy is moved to a single frame whichincreases the flickering but reduces the blur. The relative distributionof energy based upon motion improves image quality.

An alternative embodiment is using motion estimation. The window isaligned with the motion vector. This approach reduces the window sizeand preserves the contrast in the non motion direction, but thecomputation of motion vector may be more complex than merely motiondetection.

Since the PSF spread of BLE is larger than the BLE spacing to provide amore uniform backlight image, there is considerable crosstalk betweenthe BLE elements that are located close together. An iterativede-convolution algorithm may be used to derive the BLE driving value.Once the BLE driving value is determined, it is stored in a frame memorysend to the BLE (e.g. LED) driver one row at a time. The backlightdistribution may be predicted by the convolution of the BLE drivingvalue and the point spread function of the BLE. Once the backlightdistribution is calculated, the LCD value is derived by dividing theinput image by the backlight.

Referring to FIG. 14, another technique for controlling the light outputof the display is to include a layer of selectively generallytransparent material, which is preferably separated into a plurality ofrows, that selectively modifies the transmission of light through itbased upon the application of an electrical signal. Referring to FIG.15, in a first “off” state, without the application of an electricalvoltage to the transparent material, the refractive index of thetransparent material, such as liquid crystal balls is different from thesurrounding media which causes scattering or changing direction ofimpeding light. This scattering produces FTIR and light is extractedfrom the waveguide. Thus, all the regions of the display associated withthe transparent material being in an on-state (e.g., no appliedelectrical voltage) will tend to be brightened due to light extractionin that region. Referring to FIG. 15 in a second “on” state, with theapplication of an electrical voltage to the transparent material, therefractive index in the LC ball matches the surrounding media, thus thetransparent material tends to pass the light incident thereon throughwithout scattering or otherwise impeding the transmission of lightthrough it. Thus, all the regions of the display associated with thetransparent material being in an off-state (e.g., applied electricalvoltage) will tend to be otherwise darkened due TIR.

Referring to FIG. 17, the transparent material may be made from a liquidcrystal based film 400 that is sandwiched between two layers oftransparent conductive film 402 and 404. The transparent conductivefilms 402 and 404 are typically sandwiched between been a pair of glasssheets 406 and 408. Referring to FIG. 18, the liquid crystal based filmincludes a polymer matrix with liquid crystals therein. With theapplication of an electrical signal to one or more of the conductivefilms 402 and 404, the transparent material is in the “off” state.Without the application of an electrical signal to the conductive films402 and 404, the transparent material is in the “on” state. It ispossible to change the “on” and “off” state by changing the relativerefractive index of the LC and its surrounding media.

The preferred configuration of the transparent material operates basedupon a 100 volt 50/60 hertz signal. In the off state the parallel lighttransmission may be 75% light transmittance, with 7.5% haze, while inthe on state the parallel light transmission may be 74% lighttransmittance with 94% haze.

The terms and expressions which have been employed in the foregoingspecification are used therein as terms of description and not oflimitation, and there is no intention, in the use of such terms andexpressions, of excluding equivalents of the features shown anddescribed or portions thereof, it being recognized that the scope of theinvention is defined and limited only by the claims which follow.

1. A display comprising: (a) a liquid crystal layer; (b) a backlightthat provides light to said liquid crystal layer; (c) said liquidcrystal layer selectively modifying the transmission of light from saidbacklight to the front of said display; (d) said backlight includes aplurality of spaced apart light waveguides; (e) said display includes aplurality of selection elements associated with said light waveguidesthat selectively inhibit the transmission of light toward said liquidcrystal layer; (f) wherein the combination of said waveguides and saidselection elements provide light to said front of said display in atemporal manner during a frame.
 2. The display of claim 1 wherein saidplurality of said waveguides are arranged in a parallel arrangement withrespect to one another.
 3. The display of claim 2 further including alight steering mechanism that selectively directs light to at least one,and less than all, of said light waveguides at any particular time. 4.The display of claim 3 wherein at least one of said selection elementsis associated with a respective one of said plurality of waveguides. 5.The display of claim 4 wherein for a respective one of said plurality ofwaveguides that light is only substantially emitted from said respectiveguide at a position associated with a selected respective one of saidselection elements.
 6. The display of claim 5 wherein said combinationresults in a temporal multiplexed illumination of said display.
 7. Thedisplay of claim 1 wherein said selection elements includes liquidcrystal material in a polymer matrix.
 8. The display of claim 7 whereinsaid liquid crystal material in said polymer matrix is sandwichedbetween conductive layers.
 9. The display of claim 8 wherein saidtransmission is based upon the application of a voltage to at least oneof said conductive layers.
 10. The display of claim 1 wherein saidbacklight includes a plurality of light emitting diodes that provideslight to respective said waveguides.
 11. The display of claim 1 whereinsaid backlight includes a plurality of one-dimensional said waveguides.12. The display of claim 1 wherein said selection elements are lightextractors.
 13. The display of claim 1 wherein said selection elementsuse frustrated total internal reflection.
 14. The display of claim 1wherein said selection elements include micro optical structures. 15.The display of claim 6 wherein said micro optic structures include athin film layer forming a lens and shutter.
 16. The display of claim 1wherein said temporal aspect of said combination results in a decreasein motion blur.
 17. The display of claim 1 wherein a plurality of saidwaveguides extend across the entire said display.
 18. The display ofclaim 11 wherein said light steering mechanism is scanned from top tobottom of said display.
 19. The display of claim 11 wherein said lightsteering mechanism includes a mechanical shutter.
 20. The display ofclaim 1 wherein regions of an image to be displayed that is determinednot to have motion have a slower rate of providing light to saidwaveguides than regions of said image to be display that is determinedto have motion.
 21. A display comprising: (a) a liquid crystal layer;(b) a backlight that provides light to said liquid crystal layer; (c)said liquid crystal layer selectively modifying the transmission oflight from said backlight to the front of said display; (d) saidbacklight includes a plurality of spaced apart light waveguides arrangedin a one-dimensional parallel array extending from one side to the otherside of said display; (e) said backlight includes at least one lightsource associated with each of said waveguides; (f) said displayincludes a plurality of selection elements associated with each of saidwaveguides such that selective activation of one of said selectionelements results in light not being substantially inhibited that isdirected light toward said liquid crystal layer while light issubstantially inhibited that is directed toward said liquid crystallayer where one of said selection element is not selected; (g) saidselection elements include liquid crystal material in a polymer matrixsandwiched between conductive layers; (h) each of said waveguides areprovided with light in a sequential manner while a plurality ofassociated selection elements for each of said waveguides are selectedso that light is selectively emitted from each of said respectivewaveguide.
 22. The display of claim 21 wherein regions of an image to bedisplayed that is determined not to have motion have a slower rate ofproviding light to said waveguides than regions of said image to bedisplay that is determined to have motion.